The present invention relates to a stopper for mounting a flat cable to a switch body of a manipulation switch located on a steering wheel. The present invention also pertains to a mounting structure of a flat cable using the stopper.
Recently, typical automobiles are equipped with devices such as car audio equipment and hands-free mobile phones, which are operated by remote control using manipulation switches. The manipulation switches are arranged on the left and right sides of a pad located on a steering wheel. For example, a set of manipulation switches for car audio equipment is arranged on the left side of the steering wheel and a set of manipulation switches for a hands-free mobile phone is arranged on the right side of the steering wheel. Each set of manipulation switches is mounted on a switch body, which is arranged on the left side or the right side of the pad on the steering wheel. The switch bodies are electrically connected to each other by a flexible flat cable, which is arranged in the steering wheel. More specifically, connectors are arranged on the ends of the flat cable. Each connector is inserted in a connector housing, which is arranged in the corresponding switch body.
The above mentioned flat cable does not have any structure for securing the flat cable to the steering wheel other than the connectors, which are located on the ends of the flat cable. Therefore, if any of the connectors is caught on a component that constitutes the steering wheel when assembling the steering wheel, the connector could be disconnected. Therefore, the flat cable is secured at a portion other than the ends of the flat cable. For example, engaging holes are formed in the flat cable at predetermined intervals and engaging projections are formed on the switch bodies. When the engaging projections are engaged with the engaging holes, a part of the flat cable is secured. However, the flat cable is generally required to endure a predetermined tensile load (98N). This problem is solved by reinforcing the entire flat cable such that the cable endures the predetermined tensile load. However, adding a reinforcing member or increasing the thickness of an insulating coating of the flat cable not only increases the cost but also increases the size of the flat cable.
To prevent the flat cable from being damaged, a portion of the insulating coating of the flat cable is extended sideways to form a flange and an engaging hole is formed in the flange. That is, the engaging hole and the engaging projection are engaged at a portion away from core wires of the flat cable. In this case, even when the tensile load is applied to the flat cable, the insulating coating of the flat cable is prevented from being damaged.
However, such structure causes other problems. Since the flange having the engaging hole is integrally formed with the insulating coating of the flat cable, the position of the flange is determined in advance. Therefore, to adjust the flange to the engaging projection of the steering wheel, the flat cable is cut by a predetermined length. This adjusts the position of the engaging hole with respect to the engaging projection. This method causes a lot of wasted flat cable, which reduces yields.
Accordingly, it is an objective of the present invention to attach a flat cable to a switch body at low cost. It is also an objective of the present invention to provide a flat cable that sufficiently endures the tensile load. The further objective of the present invention is to provide a flat cable that can be cut at any position to improve yields.
To achieve the above objective, the present invention provides a structure for mounting a flat cable to a steering wheel. The flat cable is electrically connected to a switch body. The switch body includes a manipulation switch for operating a device that is installed in an automobile by a remote control. The mounting structure includes a stopper and an engaging projection. The stopper is adhered to the flat cable and includes a flange at least on one end. The flange extends sideways from the side edge of the flat cable. An engaging hole is formed in the flange. The engaging projection is arranged on the switch body. The engaging projection is engaged with the engaging hole of the flange.
According to the present invention, the flange extends sideways from the side edge of the flat cable. Thus, the engaging holes need not be formed in the flat cable itself. Therefore, even when the flat cable is attached to the steering wheel in a stretched state, the tensile load is mostly applied to the stopper, in which engaging hole is formed, and is not directly applied to the flat cable. Thus, the flat cable sufficiently endures the tensile load. Also, the stopper has a simple structure of adhering sheet material and is easily manufactured at low cost.
Further, the stopper is attached to the flat cable by adhering the sheet material. Therefore, the position of the stopper can be varied in the longitudinal direction of the flat cable. Therefore, the flat cable can be cut at any position and is used fully. As a result, the flat cable is not wasted, which improves yields. The sheet material is adhered by heat welding, ultrasonic welding, or by an adhesive if the sheet material is made of, for example, synthetic resin.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.